Processing of semi-conductor wafers into finished electronic components typically requires many processing steps where the wafers must be handled and processed. The wafers are very valuable, are extremely delicate, and are easily damaged by physical and electrical shocks. In addition, successful processing requires the utmost in cleanliness, free of particulates and other contaminants. As a result, specialized containers or carriers have been developed for use during processing, handling and transport of wafers. These containers protect the wafers from physical and electrical hazards, and are sealable to protect the wafers from contaminants. It is important that the containers remain sealed when in use to prevent damage to the wafers from contaminants. It is also important from a process efficiency standpoint that carriers be easily useable and cleanable.
Also, assembly processes should be as simple as possible and involve as few components as possible. Moreover it is desirable to eliminate or minimize any metallic components in the carriers and in particular the components of the latching mechanism.
The size of wafers being processed is increasing. Although processing of 150 mm wafers and smaller is still implemented, there is now a significant presence of fabrication facilities that handle 300 mm wafers. The 300 mm wafer containers deal with problems unforeseen in the containers for smaller wafers. An entire new genre of wafer containers were developed for handling the 300 mm wafers, see for example: U.S. Pat. Nos. 8,276,759; RE38221; RE42402; RE40513; 7,422,107; 7,677,393; and 6,464,081, all of which are owned by the applicant and all hereby incorporated by reference herein except for express definitions and patent claims contained therein. The basic configuration is a front opening container that has a door that fits into a door frame defining the door opening. In an x-y-z coordinate system (FIG. 1), the wafers are inserted and removed in along the y coordinate, upward and downward are along the z coordinate, and left and right are along the x coordinate. The door is inserted in a y direction and has latch tips that move along the y coordinate and then the z coordinate to both latch and pull in the door toward the container portion to constrain wafers and provide sealing between the door and container portion.
Presently, 450 mm fabrication facilities are being developed and the containers for same are also proceeding with further and different performance and functionality enhancements beyond prior art containers. Such containers can have a similar configuration of the front opening door.
Wafer containers for 150 mm and 300 mm provide various configurations of door enclosures and latching mechanisms. Many or most known latching mechanisms for 300 mm wafer containers use rotary members with robotic interfaces for actuating the latch. Typically rotatable plates include cam surfaces and a link or links with a cam follower to engage the rotatable plate. The opposite ends of the links will have or be connected to latching tips that engage with the door frames in the container portions. Latching mechanisms with components that engage and rub against other components can generate particles which are inimical to wafer processing.
In containers for larger wafers, particularly 450 mm wafers, forces are required to secure the wafers in place (i.e., forces are exerted on the forward and rear wafer cushions or restraints positioned on the door and rear of the containers are required to provide greater securement forces). Moreover, substantially more gasket length is associated with the door on the 450 mm compared to the 300 mm door. The gasket has to be compressed for sealing and the greater length directly correlates with increased closure force requirements. With these greater forces, door latching becomes more difficult. In addition to securing the door in the door frame, the latching mechanism moves the door towards the interior of the container capturing and resiliently restraining the wafers between the resilient cushions on the inside surface of the door and the rearward wafer engagement and compressing the gasket. Such capturing and sealing requires deflection of the resilient wafer cushions and compression of the gasket. The doors accomplish latching typically by automated robotic means turning robotic latch keys in key holes in the latch plates.
The required increased wafer restraint forces and gasket sealing forces with bigger doors generates higher stresses on components as well as greater frictional forces between engaged rubbing components. All this causes greater torque requirements to actuate the door closings and associated greater particulation issues between rubbing or sliding components. Industry standards and/or customer requirements dictate the forces available to accomplish the rotation for latching doors. Conventionally configured latches used for 300 mm containers and smaller do not appear to be ideally suited for the use in the larger 450 mm containers due to the additional demands discussed above.
A rotatable latching member that pivots at the periphery of the door is known such as by U.S. Pat. No. 6,457,598 as well as a single internal slot connected to latch arm. Such arrangements as illustrated are not believed provide the reduced torque requirements as needed for 450 mm wafer containers.
Conventional rotatable plates have used slots with cam followers that have sliding surfaces that engage a slot in the plate to move the linkage to accomplish the required two dimensional motion of the latch tips. It is desirable in the mechanisms to have motions that are well defined and smooth operating to prevent jams or rough operations which can lead to particle generation or ineffective or inconsistent performance. Peripheral edge engagement of a cam plate by a roller cam follower in a wafer container door mechanism is known but requires a spring to maintain engagement between the roller and cam surface of the cammed plate. It is also highly desirable to have mechanisms of minimal numbers of components, easily assembled with no or minimal tools, or robotically, and that are readily cleaned.